I/O Efficient Dynamic Data Structures for Longest Prefix Queries

Moshe Hershcovitch, Haim Kaplan

Abstract: We present an efficient data structure for finding the longest prefix of a query string p in a dynamic database of strings. When the strings are IP-addresses then this is the IP-lookup problem. Our data structure is I/O efficient. It supports a query with a string p using $O(\log_{B}(n)+\frac{|p|}{B})$ I/O operations, where B is the size of a disk block. It also supports an insertion and a deletion of a string p with the same number of I/O’s. The size of the data structure is linear in the size of the database and the running time of each operation is O(log(n) + |p|).